1. Field of the Invention
The present invention relates to a switching power supply system for automatically regulating a circuit operating frequency and the method thereof, and particularly, to a switching power supply system adapted to a computer system and capable of automatically regulating a circuit operating frequency, and the method thereof.
2. Description of the Related Art
Referring to FIG. 1, a schematic block diagram of a conventional switching power supply system is shown. The switching power supply system employs pulse width modulation (PWM) technology to control a power switch (not shown) in a DC converter 11 and supplies power to the system through a filter network 13.
According to the pulse width modulation (PWM) technology, an oscillator circuit 17 provides a signal with constant frequency to a pulse width modulation unit 15. Meanwhile, a comparator 12 detects the DC voltage at the output terminal. If the voltage obtained by dividing the DC voltage at the output terminal through a voltage divider network 14 becomes lower than a reference voltage 16, that is, if the output loading becomes heavy, then output square waves from the pulse width modulation unit 15 will be widened, which means a duty cycle of the power switch (not shown) will be increased. Thereby, compensation for the output voltage is provided to bring the output voltage back to the original rating value and thus the output voltage can be stabilized.
Similarly, if the loading becomes low, then the comparator 12 will detect that the voltage obtained by dividing the DC voltage at the output terminal through the voltage divider network 14 is greater than the reference voltage 16, and therefore the duty cycle of the output square waves from the pulse width modulation unit 15 will be reduced, which means the duty cycle of the power switch will be reduced. Thereby, the output DC voltage will be lowered to the original rating value and thus stabilized. In this circuit, the operating frequency of the power switch (not shown) does not vary with the change of the duty cycle. In other words, the circuit operating frequency always stays constant.
At present, the pulse width modulation (PWM) technology is utilized in a computer system to supply power required for the operation of a central processing unit (CPU). For the reason described above, operating frequency from the pulse width modulation PWM in a power supply system for the central processing unit (CPU) always stays constant and cannot be changed after the design is made.
Consequently, once the design is complete, the operating frequency from the pulse width modulation PWM cannot be changed in response to any current load variations resulting from execution of any software by any type of central processing unit (CPU), environmental variations inside/outside the housing and voltage variations caused by the power supply or by the load. Therefore, it is impossible to contribute anything to operating efficiency enhancement of pulse width modulation PWM, reduction in switching loss, suppression of system temperature, improvement of sawtooth current and decrease in peak-to-peak ripple voltage. Accordingly, the output voltage and the whole system are unstable, and the efficiency of the components cannot be maximized, which seriously impacts the performance of the computer.